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*Not sure whether to put this on Phy or chem.. *

What exactly happens when you light an incense stick? Inscense Stick

How is this different from a candle, or embers for that matter?

From what I understand, a candle-flame is..... well.... basically a flame and embers are pieces of glowing hot coal or wood, but then where does the lit portion of an incense stick fit in?

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In a candle, the wax first melts, then turns into a vapor above the wick and the oxidation region, where the vaporized fuel mixes with air, surrounds the central, cooler region. You can demonstrate this by extinguishing a candle and then relighting the smoke above the candle... the flame will flash back to the wick. This "flash-back" can be hazardous in a lab using ether, since a nearby flame can ignite the fumes which will burn back to the ether can.

Incense, smoldering cotton and similar combustion relies on thermal degradation of a solid, producing a narrow flame-front on the surface of the solid fuel. Since oxygen cannot penetrate the solid, the rate of combustion is limited. For that reason, cotton bales burn slowly but are very difficult to extinguish, since the interior remains hot and water cannot quickly penetrate. On the other hand, stretching a cosmetic cotton ball changes the burning from smoldering to an intense flame.

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  • $\begingroup$ Wow! never knew about flashback. So basically inscense is like a candle withless exposed surface area which causes it to burn slowly? Or is it a decomposition reaction? $\endgroup$ – Srathi00 Sep 8 '16 at 13:24
  • $\begingroup$ Again, candles have solid fuel converting to gaseous fuel, so the solid wax is not burning, just the mixture of fuel in air. Incense burns at the surface of the solid fuel. $\endgroup$ – DrMoishe Pippik Sep 8 '16 at 13:49

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